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26 .\" from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology --
27 .\" Portable Operating System Interface (POSIX), The Open Group Base
28 .\" Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of
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43 .Nd "lock a semaphore"
50 .Fn sem_timedwait "sem_t *sem" "const struct timespec *abs_timeout"
52 .Fn sem_clockwait_np "sem_t * restrict sem" "clockid_t clock_id" "int flags" "const struct timespec * rqtp" "struct timespec * rmtp"
56 function locks the semaphore referenced by
61 However, if the semaphore cannot be locked without waiting for
62 another process or thread to unlock the semaphore by performing
65 function, this wait will be terminated when the specified timeout expires.
67 The timeout will expire when the absolute time specified by
69 passes, as measured by the clock on which timeouts are based (that is,
70 when the value of that clock equals or exceeds
73 absolute time specified by
75 has already been passed at the time of the call.
77 Note that the timeout is based on the
83 is not checked if the semaphore can be locked immediately.
87 function is a more flexible variant of
91 parameter specifies the reference clock.
96 then the requested timeout
98 is an absolute timeout; otherwise,
99 the timeout is relative.
100 If this function fails with
102 and the timeout is relative,
105 will be updated to contain the amount of time remaining in the interval
107 the requested time minus the time actually slept
109 An absolute timeout has no effect on
111 A single structure can be used for both
117 functions return zero if the calling process successfully performed the
118 semaphore lock operation on the semaphore designated by
120 If the call was unsuccessful, the state of the semaphore is unchanged,
121 and the function returns a value of \-1 and sets the global variable
123 to indicate the error.
125 These functions will fail if:
130 argument does not refer to a valid semaphore, or the process or thread would
131 have blocked, and the
133 parameter specified a nanoseconds field value less than zero or greater than
134 or equal to 1000 million.
136 The semaphore could not be locked before the specified timeout expired.
138 A signal interrupted this function.
151 function is not specified by any standard;
154 at the time of this writing.
158 function first appeared in
162 function first appeared in